Apparatus for measuring hardness of materials

ABSTRACT

An apparatus for measuring hardness of materials has an indentor to be pressed into the surface of material, a rod in the form of a center plate having a shank rigidly secured to one end thereof and the indentor rigidly secured to the other end thereof. The apparatus also has a dynamometric gauge having a first branch thereof with a hole in which the shank of the rod is received. A second branch of the dynamometric gauge supports a spindle of a device for loading the indentor. One of the branches of the dynamometric gauge carries at least one pick-up for measuring the load at the indentor engageable with the other branch of the dynamometric gauge. The apparatus also has a device for measuring the depth of penetration of the indentor into the surface of material in the form of a frame having its opposed bars enclosing the first branch of the dynamometric gauge. A tip is rigidly secured to the first bar of the frame located between the surface of material and the first branch of the dynamometric gauge, the indentor being received in the tip. The first branch of the dynamometric gauge carries a pick-up for measuring the depth of penetration of the indentor into the surface of material engageable with the frame.

This invention relates to the field of investigation into physicalproperties of materials, and more specifically, it deals withapparatuses for measuring hardnesses of materials.

The invention will find application in determining mechanical propertiesof metal in the casing of a nuclear power reactor during the wholeservice life.

BACKGROUND OF THE INVENTION

Known methods of determining mechanical properties of solids are basedon experimental relationships of mechanical properties versus hardnessof materials. A hard alloy member in the form of a sphere or cone iscaused to penetrate the surface of an object being studied to produce animpression. Hardness of materials is determined as the ratio of a forcepressing the indentor to the area of the impression or depth ofpenetration of the indentor into the surface of material. Usingexperimental formulae for calculations, standard mechanical propertiessuch as ultimate strength and yield limit are determined from thehardness value. If the configuration of the impression is determinedusing optical test equipment after the load has been relieved from thesurface of material, accuracy of hardness measurement is low since afterthe load removal from the surface of the material the configuration ofthe impression changes so as to lower accuracy of hardness measurement.

With an automatic measurement of the depth of penetration of theindentor into the surface of material during penetration of the indentorunder a preset load it is not possible to record a complicated mode ofmaterial deformation, i.e. the relationship of the load at the indentorversus the depth of penetration of the indentor into the surface ofmaterial and penetration time. This method does not allow delicateprocesses of deformation in the indent to be studied thus substantiallyreducing informativity of the method.

Widely known in the art is an automatic durometer (see, e.g. U.S.S.R.publication 170721), comprising a dynamometric gauge having a firstbranch having a composite rod consisting of a pair of vertical movableparts mounted for movement along guides of an inner movable cylinder.The inner movable cylinder is mounted for movement along guides of afixed outer cylinder, the inner cylinder being biased by a spring withrespect to the outer cylinder. A stop washer is biased by a spring tothe end of the inner movable cylinder and encloses an indentor which issecured to the lower vertical part of the composite rod. Displacement ofthe indentor with respect to the stop washer is measured by means of adial gauge mounted on the fixed outer cylinder and engageable with thelower vertical part of the composite rod. The apparatus also comprises acasing accommodating an indentor loading means having a spindle securedto the second branch of the dynamometric gauge and a drive for movingthe spindle.

The main load of the indentor is recorded by means of an electriccontact pick-up mounted on the second branch of the dynamometric gaugeand cooperating with the first branch of the dynamometric gauge.

The preload is recorded by means of an electric contact pick-up providedbetween the first branch of the dynamometric gauge and the spindle ofthe drive for moving the spindle cooperating with the second branch ofthe dynamometric gauge.

The prior art apparatus functions automatically and allows hardness ofmaterials to be measured with a high enough accuracy, but it cannotensure continuous recording of load and depth of penetration of theindentor into the surface of material so as to result in a low accuracyof measurement of hardness of materials. The use of the apparatus forobjects located in radioactive zones is difficult because deactivationand maintenance of the apparatus are complicated owing to thecomplicated structure and presence of cavities. Rapid assembly anddisassembly as well as setup of the apparatus under radiation conditionsare associated with high radiation exposure of operating personnel. Theprovision of the two coaxially mounted cylinders and composite rod ofthe indentor cooperating along parallel lines of guides with appropriatefree fits lowers accuracy of measurement of hardness of materialsespecially in various positions of the apparatus in space where it isnecessary to measure hardness of vertical or inclined surfaces ofvarious parts. The apparatus does not allow delicate processes ofdeformation of materials to be studied.

Widely known in the art is a portable device for measuring Brinellhardness of materials (Yu. A. Mayorov, F. M. Nikitin, Instruments forHardness Measurements (in Russian), 1982, Mashinostroenie PublishingHouse, Moscow. pp. 17-19; 54-55), comprising an indentor to be pressedinto the surface of material and a rod in the form of a center platehaving a shank at one end thereof and the indentor rigidly secured tothe other end thereof. A dynamometric gauge is mounted perpendicularlywith respect to the surface of material, one branch of the gauge havinga hole in which the rod shank is received. The device also comprises ameans for loading the indentor having a spindle mechanically coupled toa drive for its movement and mounted coaxially with the rod on the otherbranch of the dynamometric gauge. The means for loading the indentor ismounted in a casing. The rod shank is engageable with a means formeasuring the load of the indentor or a dial gauge mounted on thecasing.

The device also comprises a means for attaching the device to an objectfor measurements and an optical means for measuring the diameter ofimpression in the material, e.g. a microscope. This device allows thefinal result of deformation of the surface of material such asimpression or indent to be recorded so that it features a lowinformativity as regards processes of elastic and plastic deformation ofmaterial in the indent and a low accuracy. The device cannot be used forobjects located in zones with high radiation as it cannot functionautomatically and calls for a permanent attendance of personnel so as toresult in an increase in radiation exposure of the personnel.

SUMMARY OF THE INVENTION

It is an important object of the invention to enhance accuracy inmeasuring hardness of materials.

Another object of the invention is to enlarge functional capabilities ofthe apparatus and facilitate operation and maintenance of the apparatus.

These objects are accomplished by that an apparatus for measuringhardness of materials, comprising an indentor to be pressed into thesurface of material, a rod in the form of a center plate having a shanksecured to one end thereof and the indentor rigidly secured to the otherend thereof, a dynamometric gauge having a longitudinal plane ofsymmetry thereof extending perpendicularly with respect to the surfaceof material, a first branch having a hole in which the rod shank isreceived, a means for loading the indentor having a spindle mechanicallycoupled to a drive for its movement and mounted on the second branch ofthe dynamometric gauge coaxially with the rod, a casing supporting themeans for loading the indentor, and at least one pick-up for measuringthe load at the indentor mechanically coupled to one of the branches ofthe dynamometric gauge and having its sensor member engageable with theother branch of the dynamometric gauge, according to the invention,comprises a means for measuring the depth of penetration of the indentorinto the surface of material which is in the form of a frame having itsopposed bars enclosing the first branch of the dynamometric gauge andmounted for movement along the axis of the rod on the center plate androd shank, respectively, an annular tip having one end thereof rigidlysecured to the first bar of the frame located between the surface ofmaterial and the first branch of the dynamometric gauge, the indentorbeing received in the tip in a spaced relation thereto and the other endof the tip being engageable with the surface of material, the apparatusalso comprising at least one pick-up for measuring the depth ofpenetration of the indentor into the surface of material which ismechanically coupled to the first branch of the dynamometric gauge andwhich has its sensor member engageable with the frame of the means formeasuring the depth of penetration of the indentor into the surface ofmaterial.

To facilitate manufacture, installation and maintenance of theapparatus, it is preferred that the frame of the means for measuring thedepth of penetration of the indentor into the surface of material bepositioned with respect to the dynamometric gauge in such a manner thattheir longitudinal planes of symmetry be perpendicular with respect toeach other.

To facilitate maintenance of the apparatus, it is preferred that centralholes be provided in the opposed bars of the frame for measuring thedepth of penetration of the indentor into the surface of material toaccommodate bearings and to receive the center plate and the rod shank,respectively.

To enhance accuracy of measurement of hardness of materials, it ispreferred that use be made of at least two pick-ups for measuring theindentor load and two pick-ups for measuring the depth of penetration ofthe indentor into the surface of material, the pick-ups for measuringthe indentor load and the pick-ups for measuring the depth ofpenetration of the indentor into the surface of material beingpositioned on either side of the longitudinal plane of symmetry of thedynamometric gauge.

To enhance accuracy of measurement of hardness of materials, facilitatemanufacture, installation and maintenance, it is preferred that theapparatus comprise a first auxiliary outside member supported on one ofthe branches of the dynamometric gauge and having at least one main holein which at least one indentor load pick-up is rigidly secured, a secondoutside member supported on the other branch of the dynamometric gaugeand having at least one contact land engageable with the sensor memberof at least one indentor load pick-up, a third outside member supportedon the first branch of the dynamometric gauge and having at least onemain hole thereof in which at least one pick-up for measuring the depthof penetration of the indentor into the surface of material is rigidlysecured, and a fourth outside member supported on the first bar of theframe of the means for measuring the depth of penetration of theindentor into the surface of material having at least one contact landengageable with the sensor member of at least one pick-up for measuringthe depth of penetration of the indentor into the surface of material.

For enhancing accuracy of measurement of hardness of materials, it ispreferred that at least one of the outside members have an auxiliaryhole for receiving one end of at least one guide pin having the otherend thereof journalled in a bearing which is received in at least oneperipheral hole of one of the bars of the frame of the means formeasuring the depth of penetration of the indentor into the surface ofmaterial.

To enhance accuracy of measurement of hardness of materials in using atleast two guide pins, it is preferred that the pins be positioned oneither side of the longitudinal axis of symmetry of the dynamometricgauge.

To enhance accuracy of measurement of hardness of materials, it ispreferred that the apparatus comprise an elastic member having itsopposed sides secured to the spindle of the means for loading theindentor on the side of the inner surface of the second branch of thedynamometric branch and to the second bar of the frame of the means formeasuring the depth of penetration of the indentor into the surface ofmaterial, located between the first and second branches of thedynamometric gauge.

To enhance accuracy of measurement of hardness of materials, it ispreferred that the elastic member comprise an annular spring.

To ensure remote control of the apparatus, it is preferred that thepick-ups for measuring the indentor load, the pick-ups for measuring thedepth of penetration of the indentor into the surface of material, andthe drive for moving the spindle of the means for loading the indentorbe electrical.

To enhance accuracy of measurement of hardness of materials, it ispreferred that the means for loading the indentor also comprise a wormgearing connected to the electric drive for moving the spindle and aball-and-screw gearing operatively connected to the worm gearing andprovided on the periphery of the spindle.

Owing to the employment of the means for measuring the depth ofpenetration of the indentor into the surface of material, comprising theframe connected to the center plate and to the rod shank, the inventionallows plays in the free fit to be eliminated and lowers spuriouselastic deformation of the rod so as to enhance accuracy of measurementof hardness of materials and facilitate installation, manufacture andsetup of the apparatus. The apparatus has a minimized number ofcomponents the major part of which are mounted coaxially with, andsymmetrically with respect to the rod thus also facilitatinginstallation, manufacture and setup of the apparatus.

DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to specificembodiments of the apparatus for measuring hardness of materialsaccording to the invention illustrated in the accompanying drawings, inwhich:

FIG. 1 is a general view (front elevation, partially in longitudinalsection) of an apparatus for measuring hardness of materials showingmembers for attaching the apparatus to the surface of material accordingto the invention;

FIG. 2 is a general view (side elevation in longitudinal section) of anapparatus according to the invention;

FIG. 3 is a kinematic diagram of an apparatus according to theinvention;

FIG. 4 is a sectional view taken along line IV--IV in FIG. 2 (in a planview) according to the invention;

FIG. 5 is a means for measuring the depth of penetration of an indentor(side elevation) according to the invention;

FIG. 6 is ditto of FIG. 5 (plan view) according to the invention;

FIG. 7 is ditto of FIG. 5 (front elevation) according to the invention;

FIG. 8 is a sectional view taken along line VIII--VIII in FIG. 2 (a planview) according to the invention;

FIG. 9 is an electrical block-diagram of an apparatus for measuringhardness of materials according to the invention.

PREFERRED EMBODIMENT

An apparatus for measuring hardness of materials is attached to asurface 1 of material (FIG. 1) by means of a support structureconsisting of a bed 2 which is secured to the surface 1 of material bymeans of two or more pairs of electromagnets 3. Shoes 4 are secured tothe ends of the electromagmets 3 and are biased by springs 6 withrespect to a base 5 for rotation about an axis 7. A movable carriage 8is mounted on the bed 2 for movement along guide planes 9 of the bed 2by means of balls 10. The apparatus for measuring hardness of materialscomprises an indentor 11 (FIG. 2) to be pressed into the surface 1 ofmaterial in the form of a ball. The apparatus also has a rod 12 in theform of a center plate 13 having an indentor 11 secured to one endthereof and a shank 14 secured to the other end thereof. The shank 14 ofthe rod 12 is retained by means of a key 15 in a hole 16 of a firstbranch 17 of a diynamometric gauge 18 which is positioned in animmediate vicinity to the surface 1 of material. The dynamometric gauge18 is positioned in such a manner that the longitudinal axis of symmetryof the dynamometric gauge 18 extends perpendicularly with respect to thesurface 1 of material.

Mounted on a second branch 19 of the dynamometric gauge 18 to extendalong an axis 20 of the rod 12 is one end of a spindle 22 of a means forloading the indentor retained by means of a key 21. The means forloading the indentor comprises a drive for moving the spindle in theform of an electric motor 23 (FIG. 3) mechanically coupled to thespindle 22 by means of a worm gearing 24. The worm gearing 24 comprisesa worm 25 mechanically coupled to a shaft 26 of the electric motor 23.The worm 25 meshes with a gear 27 having a bushing 28 received in itsbore. The gear 27 and the bushing 28 are made to form a non-detachablejoint. The bushing 28 is journalled by means of bearings 29 on an innersurface 30 of a casing 31. A pin 32 is provided on the periphery of thespindle 22 to move in a longitudinal groove 33 made in the inner surface30 of the casing 31.

The spindle 22 is received in a bore 34 of the bushing 28. Providedbetween a helical inner surface of the bore 34 of the bushing 28 and ahelical periphery of the spindle 22 there is a ball-and-screw gearing inthe form of a set of balls 35. The frame of the electric motor 23 isattached to an outer periphery 36 of the casing 31 by means of fasteners37. The shaft 26 of the electric motor 23 is journalled by means ofbearings 29 on the inner surface 30 of the casing 31. The upper outersurface 38 of the casing 31 is removably received in a groove 39(FIG. 1) of an inner surface 40 of the carriage 8 by means of severalangle irons 41 each having its flanges 42 adjoining to the outerperiphery 36 of the casing 31 and inner surface 40 of the carriage 8 andsecured to these surfaces 36, 40 by means of washers 43 and bolts 44.

An outside member 46 is attached to an inner side 45 (FIG. 2) of thesecond branch 19 of the dynamometric gauge 18 and is made in the form ofa plate secured to the spindle 22 to extend perpendicularly with respectthe axis 20 of the rod 12, clamps 47 (FIG. 4) being provided at the endsof the plate. The clamps 47 have holes 48, and stop screws are used toclamp bodies of indentor load pick-ups 50 in these holes to extend inparallel with the axis 20 of the rod 12 on either side of thedynamometric gauge 18.

The apparatus also comprises a means for measuring the depth ofpenetration of the indentor into the surface of material comprising aframe 51 (FIG. 2) having its opposed bars 52, 53 enclosing the firstbranch 17 of the dynamometric gauge 18.

The first bar 52 of the frame 51 located between the surface 1 ofmaterial and the first branch 17 of the dynametric branch 18 is made inthe form of a plate having a tapering bottom side. The first bar 52 ofthe frame 51 has a hole 54 (FIGS. 2,5) coaxial with the rod 12. Anannular tip 55 is threaded into the hole 54 on the side of the surface 1of material (FIG. 2), and the indentor 11 is received in the tip in aspaced relation thereto. A bearing 56 having its inner bore receivingthe center plate 13 of the rod 12 is received in the hole 54 of thefirst bar 52 of the frame 51 on the opposite side thereof. A pair ofsymmetrically positioned holes 57 (FIGS. 2, 6) are made in the peripheryof the first bar 52 of the frame 51 to receive bearings 58 (FIG. 2)which are made in the form of bushings each having its bore in which oneend of each guide pin 59 is received, the guide pins running in parallelwith the axis 20 of the rod 12. Outside members 60 (FIGS. 2,5) areprovided as integral parts of, and at the ends of the first bar 52 ofthe frame 51 and have contact lands 61 on their surfaces. Stems 62 (FIG.5) are provided at the lower ends of the contact lands 61 which arereceived in holes 63 of the outside members 60 and on which adjustingnuts 64 are threaded and operatively interact with stop screws 65 (FIGS.6, 7) in a known way. The holes 63 which receive the stems 63 of thecontact lands 61 extend coaxially with the rod 12 (FIG. 2). The firstbar 52 of the frame 51 (FIGS. 5, 6, 7) is connected to the second bar 53by means of an arcuated lateral plate 66 having its curved portionlocated beyond the lateral side of the first bar 52 of the frame 51.

The second bar 53 (FIGS. 5, 6) of the frame 52 located between the firstand second branches 17, 19 (FIG. 2) of the dynamometric branch 18 is inthe form of a plate having a groove 67 (FIGS. 2, 5, 6) in its outer sidein which an elastic member in the form of an annular spring 68 isreceived (FIG. 2). A hole 69 is made in the groove 67 of the second bar53 of the frame 51 to receive a bearing 70 in the form of a bushing. Theinner bore of the bearing 70 receives the shank 14 of the rod 12. Theannular spring 68 is positioned symmetrically with respect to the axis20 of the rod 12 has its sides secured to the spindle 22 on the side ofthe inner surface 45 of the second branch 19 of the dynamometric gauge18 and to the second bar 53 of the frame 51, respectively. One side 71of the annular spring 68 is received in a groove 73 made in a surface 74of the outside member 46 facing towards the surface 1 of material bymeans of a nut 75 and a retainer ring 76 put on the spindle 22. Theother side 72 of the annular spring 68 is secured by means of bolts 77screwed in the bar 53.

Mounted on an inner side 78 of the first branch 17 of the dynamometricgauge 18 is an outside member 79 which has a base 80 with projections 81(FIGS. 2, 8) which comprises a plate and which is attached to the innderside 78 (FIG. 2) of the first branch 17 of the dynamometric gauge 18 toextend perpendicularly with respect to the axis 20 of the rod 12.Contact lands 82 are provided on the projections 81 of the base 80 (FIG.8). A pin 83 is provided on the bottom end of each contact land 82(FIG. 1) and is received in a hole 84, an adjusting nut 85 being put onthe pin. The pin 83 interacts with a stop screw 86. Sensor members 87 ofthe pick-ups 50 for measuring the indentor load bear against the contactlands 82. The outside member 79 (FIG. 2) also has legs 88 provided onthe opposed ends of the base 80 to extend at an angle with respect tothe axis 20 of the rod 12. Clamps 89 (FIGS. 2, 4) are provided at theends of the legs 88 to extend in parallel with the axis 20 of the rod12. Main holes 90 of the clamps 89 receive bodies of pick-ups 92 (FIG.2) for measuring the depth of penetration of the indentor into thesurface of material clamped by means of stop screws 91 (FIG. 4), thesensor members 93 of the pick-ups being engageable with the contactlands 61 of the outide members 60 provided on the first bar 52 of theframe 51 positioned between the surface 1 of material and the firstbranch 17 of the dynamometric gauge 18. Auxiliary holes 94 are made inthe bottom part of each leg 88, and each guide pin 59 has its second endrigidly secured in the auxiliary hole. The base 80 of the outside member79 is attached to the innder side 78 of the first branch 17 of thedynamometric gauge 18 by means of a nut 95 threaded on the shank 14 ofthe rod 21 which is received in a central hole 96 of the base 80 of theoutside member 79.

The pick-ups 50 for measuring the indentor load and the pick-ups 92 formeasuring the depth of penetration of the indentor into the surface ofmaterial are connected in an electric circuit shown in Fig. 9. Outputsof the pick-ups 50 for measuring the indentor load and of the pick-ups92 for measuring the depth of penetration of the indentor into thesurface of material are connected to inputs of two switching devices 97,98. Outputs of the switching devices 97, 98 are connected to inputs ofsignal amplifiers 99, 100, respectively. First outputs of the signalamplifiers 99, 100 are connected to first and second inputs of atwo-coordinate recorder 101. Second outputs of the amplifiers 99, 100are connected to inputs of analog-to-digital converters 102, 103,respectively. Outputs of the analog-to-digital converters 102, 103 areconnected to inputs of a computer 104.

The apparatus for measruing hardness of materials functions in thefollowing manner.

The apparatus is used, e.g. for monitoring condition of metal in thecasing of a nuclear reactor. (not shown in the drawings). The apparatusis moved by means of handling equipment (not shown in the drawings) intothe interior space of the casing of a nuclear reactor, to a chosen spotwhere hardness of materials is to be measured, e.g. to the zone of weldof the nuclear reactor casing.

The apparatus is attached to the chosen portion of the surface 1 ofmaterial (FIG. 1) by switching on a power supply (not shown) of theelectromagnets 3 which will have their shoes attracted to the surface 1of material of the nuclear reactor casing with a force of up to 10 kN.

Measurement of hardness of materials is carried out with remote controlfrom an operator's control board by using connecting cables and aTV-camera owing to the electric drive of the spindle and to the use ofelectrical pick-ups 50 for measuring the indentor load (FIG. 2) andpick-ups 92 for measuring the depth of penetration of the indentor intothe surface of material.

The apparatus is placed in an immediate vicinity to the spot wherehardness of material is to be studied on the surface 1 (FIG. 1) of thereactor casing metal by means of the carriage 8 which is moved along theguide planes 9 of the bed 2 by means of an electric motor of thecarriage 8 (not shown in the drawings).

When the movable carriage 8 is fixed in an immediate vicinity to thespot of measurement of hardness of material, the electric motor 23 (FIG.3) of the means for loading the indentor is energized. The shaft 26 ofthe electric motor 23 rotates the worm 25 which meshes with the gear 27rotating together with the bushing 28 in the bearings 29. the shaft ofthe electric motor 23 rotates at a speed which is chosen in accordancewith hardness of the material. Rotation of the bushing 28 through theball-and-screw gearing in the form of a set of the balls 35 ensures theaxial movement of the spindle 22 along the axis 20 of the rod so thatthe dynamometric gauge 18 moves towards the surface 1 of material untilthe tip 55 of the frame 51 of the means for measuring the depth ofpenetration of the indentor into the surface of material comes in touchwith the surface 1 of material. The use of the ball-and-screw gearing inthe form of a set of the balls 35 allows a play in the free fit betweenthe outer periphery of the spindle 22 and the inner surface of thebushing 28 of the means for loading the indentor to be eliminated so asto rule out vibrations of the spindle 22 under the action of theelectric motor 23 of the spindle rotary drive and to enhance accuracy ofmeasurement of hardness of materials.

During further movement of the spindle 22 the indentor 11 comes incontact with the surface 1 of material (FIG. 2), and the load upon thesurface 1 is then uniformly increased. When both the indentor 11 and thetop 55 of the frame 51 of the means for measuring the depth ofpenetration of the indentor into the surface of material are in contactwith the surface 1 of material, the pick-ups 50 and 92 (FIG. 4) willrecord zero values of the load at the indentor 11 (FIG. 12) and depth ofpenetration of the indentor 11 into the surface 1 of material.

Calibration and tuning of the pick-ups 50, 92 (FIG. 4) to zero valuesmust be carried out before measuring hardness of materials in alaboratory. The pick-ups 50 (FIGS. 1, 8) are tuned by means of theadjusting nuts 85 threaded on the pins 83 of the contact lands 82 so asto bring the contact lands 82 in engagement with the sensor members 87of the pick-ups 50. The pick-ups 92 (FIGS. 2, 8) are tuned by means ofthe adjusting nuts 64 threaded on the stems 62 of the contact lands 61so as to bring the contact lands 61 in engagement with the sensormembers 93 of the pick-ups 92.

For an accurate recording of zero value of the load at the indentor 11(FIG. 2) and of the depth of penetration of the indentor 11 into thesurface 1 of material, the tip 55 of the frame 51 is made in such amanner that the end face of the tip 55 protrudes beyond the vertex ofthe indentor 11 at a distance of 30 to 50 μm which depends on theprofile of the surface 1 of material and geometry of the indentor 11. qpAccurate initial position of the tip 55 of the frame 51 upon itsengagement with the surface 1 of material with respect to the vertex ofthe indentor 11 and its position in parallel with the surface 1 ofmaterial without plays of the frame 51 are achieved owing to theprovision of the elastic member in the form of the annular spring 68which compensates for weight of the frame 51. The force of the annularspring 68 is chosen in such a manner as to rule out penetration of thetip 55 of the frame 51 into the surface 1 of material.

Output signals from the pick-ups 50 (FIG. 4) for measuring the load atthe indentor and from the pick-ups 92 for measuring the depth ofpenetration of the indentor into the surface of material go to inputs ofthe switching devices 97, 98 (FIG. 9) which add the electric signals.The output signals from the switching devices 97, 98 are fed, via theamplifiers 99, 100, to the inputs of the two-coordinate recorder 101 andanalog-to-digital converters 102, 103. The analog-to-digital converters102, 103 translate the output signals of the pick-ups 50, 92 (FIG. 4)into code of the computer 104 (FIG. 9). The output signals of theanalog-to-digital converters 102, 103 are fed to the inputs of thecomputer 104 where they are stored in a memory (not shown). A chartshowing the impression of the indentor 11 (FIG. 2) into the surface 1 ofmaterial is recorded in the two-coordinate recorder 101 in the followingcoordinates: load at the indentor 11 versus depth of penetration of theindentor 11 into the surface 1 of material.

The zero values of the load at the indentor 11 (FIG. 2) and depth ofpenetration of the indentor 11 into the surface 1 of material are firstrecorded in the two-coordinate recorder 101 which corresponds to theinitial engagement of the end faces of the indentor 11 and tip 55 withthe surface 1 of material.

During a further increase in the load at the indentor 11, the indentor11 penetrates into the surface 1 of material, the dynamometric gauge 18is deformed, and the sensor members 87 (FIG. 1) of the pick-ups 50 ofthe indentor load provided on the second branch 19 of the dynamometricgauge 18 cooperate with the contact lands 82 (FIG. 8) provided on theprojections 81 of the outside member 79 secured to the first branch 17(FIG. 12) of the dynamometric gauge 18. As a result of this, values ofcurrent load at the indentor 11 are continually recorded in thetwo-coordinate recorder 101 (FIG. 9) and in the memory of the computer104.

During penetration of the indentor 11 (FIG. 2) into the surface 1 ofmaterial the dynamometric gauge 18 is deformed, and the first branch 17of the dynamometric gauge 18 cases the legs 88 of the outside member 79supporting the pick-ups 92 for measuring the depth of penetration of theindentor into the surface of material to move along the guide pins 59.The sensor members 93 of the pick-ups 92 will thus cooperate with thecontact lands 61 (FIGS. 2, 8) provided on the outside members 60 of thefirst bar 52 of the frame 51. As a result, the values of the depth ofpenetration of the indentor 11 into the surface 1 of material arecontinually recorded in the two-coordinate recorder 101 (FIG. 9) and inthe memory of the computer 104.

During penetration of the indentor 11 (FIG. 2) into the surface 1 ofmaterial and deformation of the dynamometric gauge 18 the center plate13 of the rod 12 moves in the bearings 56 of the first bar 52 of theframe 51, and the guide pins 59 move in the bearings 58 of the outsidemembers 60 so as to rule out plays between the inner surface of the hole54 of the first bar 52 of the frame 51 and the outer periphery of thecenter plate 13 of the rod 12 and to reduce a rotary play of the frame51. This ensures uniform movement of the sensor members 87, 97 of thepick-ups 50, 92 (FIG. 4) without misalignments along the axis 20 of therod 12 (FIG. 2) so as to enhance immunity of the apparatus to noise andimprove accuracy of measurement of hardness of materials.

Placing the pick-ups 50, 92 (FIG. 4) pairwise on eithe rside of thedynamometric gauge 18 ensures compensation for plays in the free fit ofthe center plate 13 (FIG. 2) and shank 14 of the rod 12 in the frame 51and enhances accuracy of measurements of hardness of materials.

During penetration of the indentor 11 into the surface 1 of material thetip 55 of the frame 51 sets up the initial level of the surface 1 ofmaterial so as to record by means of the pick-ups 92 values of the depthof penetration of the indentor 11 into the surface 1 of material withreference to the initial level of this surface 1 and to enhance accuracyof measurement of hardness of materials. The load at the indentor 11 israised to a maximum value of the load which is chosen in accordance withhardness of the material being tested, and the electric motor 23 is thenswitched off, with subsequent exposure at the maximum load, whereafterthe electric motor 23 (FIG. 3) is reversed, and the load is relievedfrom the indentor 11. The elastic member in the form of the annularspring 68 (FIG. 2) compensates for weight of the frame 51 so as to ruleout the action of the frame 51 upon the material being tested and toenhance reliability and accuracy of the apparatus.

When the indentor 11 is free from load, the apparatus is retracted fromthe surface 1 of material by means of the carriage 8 and is movedtowards another area of the surface 1 for a next measurement of hardnessof materials. After completion of measurements of hardness of materialsthe apparatus is withdrawn from the casing of the nuclear reactor andradiation monitoring and deactivation are carried out to achievepermissible radiation level. The apparatus makes it possible to monitorthe entire kinetics of local deformation of a material under the actionof the indentor through three phases of the deformation process: activeloading, exposure to a load and load relief from the indentor 11 and torecord current values of plastic and elastic deformation. The apparatusalso allows local deformation of materials to be carried out within alarge range of loads and rates of deformation; microdeformationprocesses can be studied, macro-and microcreep of materials during theexposure to a load can be recorded, elastic properties of materials andtheir energy relaxation capacity during deformation can be evaluated bythe value of elastic recovery during load relief, and deformability ofmaterials can be assessed.

After handling the data in the computer 104 (FIG. 9) values of standardBrinell hardness, Meyer hardness, ultimate tensile strength, yieldlimit, uniform deformation and other mechanical properties of materialscan be obtained so as to enlarge functional capabilities of theapparatus.

The invention allows construction of the apparatus to be simplified andradioactive exposure of personnel in operation under harmful conditionsto be lowered, and technical objects can be tested under harmfulconditions, e.g. at nuclear power plants in combination with rapidremoval and interchangeability of the apparatus. The invention makes itpossible to enlarge functional capabilities of the apparatus so that itcan be used for determining coating thickness and to test materials witha low reflectivity (polymers) and brittle materials.

We claim:
 1. An apparatus for measuring hardness of materials, saidapparatus comprising:a rod having an axis; a center plate of said rodhaving a first end and a second end; a shank of said rod having a firstend and a second end; said first end of said shank being secured to saidfirst end of said center plate of said rod; an indentor to be pressedinto a surface of material secured to the second end of said centerplate of the rod; a dynamometric gauge having a first branch and asecond branch, a longitudinal plane of symmetry which is positioned toextend perpendicularly with respect to said surface of material; thefirst branch of said dynamometric gauge having an outer surface and aninner surface and a hole in which said shank of said rod is received;the second branch of said dynamometric gauge having an outer surface andan inner surface; a means for loading the indentor accommodated in acasing; a spindle of said means for loading the indentor having aperiphery and mounted coaxially with said rod on said second branch ofsaid dynamometric gauge; a drive for moving the spindle of said meansfor loading the indentor which is mechanically coupled to said spindleof said means for loading the indentor; at least one pick-up formeasuring the load at the indentor having a body and a sensor member,the body being mechanically coupled to one of the branches of saiddynamometric gauge; said sensor member of said at least one pick-up formeasuring the load at the indentor being engageable with said otherbranch of said dynamometric gauge; a means for measuring the depth ofpenetration of the indentor into the surface of material in the form ofa frame having a first bar and a second bar opposed to each other, alongitudinal plane of symmetry, said first and second bars enclosingsaid first branch of said dynamometric gauge; said first bar of saidframe of said means for measuring the depth of penetration of theindentor into the surface of material having a central part and aperipheral part, being positioned between said surface of material andsaid first branch of said dynamometric gauge and mounted for movementalong said axis of said rod on said center plate of said rod; saidsecond bar of said frame of said means for measuring the depth ofpenetration of the indentor into the surface of material having acentral portion and a peripheral portion, being positioned between saidfirst and second branches of said dynamometric gauge and mounted formovement along said axis of said rod on said shank of said rod; a tiphaving a first end and a second end and an interior space, the first endof the tip being secured to said first bar of said frame and the secondend of tip being engageable with said surface of material; said interiorspace of said tip receiving the indentor in spaced relation thereto; atleast one pick-up for measuring the depth of penetration of the indentorinto the surface of material having a body and a sensor member, the bodybeing mechanically coupled to said first branch of said dynamometricgauge, the sensor member being engageable with said frame of said meansfor measuring the depth of penetration of the indentor into the surfaceof material.
 2. An apparatus according to claim 1, wherein said frame ofsaid means for measuring the depth of penetration of the indentor intothe surface of material is positioned with respect to said dynamometricgauge in such a manner that said longitudinal planes of symmetry thereofextend perpendicularly with respect to each other.
 3. An apparatusaccording to claim 2, comprising said frame of said means for measuringthe depth of penetration of the indentor into the surface of material;said first bar of said frame having a hole in said central portionthereof; said second bar of said frame having a hole in said centralportion thereof; a first bearing received in said hole of said first barof said frame, said center plate of said rod being journalled in saidfirst bearing; a second bearing received in said hole of said second barof said frame, said shank of said rod being journalled in said secondbearing.
 4. An apparatus according to claim 2, comprising: said at leasttwo pick-ups for measuring the load at the indentor positioned on eitherside of the longitudinal plane of said dynamometric gauge;said at leasttwo pick-ups for measuring the depth of penetration of the indentor intothe surface of material positioned on either side of said dynamometricgauge.
 5. An apparatus according to claim 2, comprising:a first outsidemember mounted on one of said branches of said dynamometric gauge; atleast one main hole in said first outside member, said body of said atleast one pick-up for measuring load at the indentor being rigidlysecured in said hole; a second outside member mounted on said otherbranch of said dynamometric gauge; at least one contact land provided insaid second outside member, said sensor of said at least one pick-up formeasuring the load at the indentor being engageable with said contactland; a third outside member mounted on said first branch of saiddynamometric gauge; at least one main hole in said third outside member,said body of said at least one pick-up for measuring the depth ofpenetration of the indentor into the surface of material being rigidlysecured in said hole; a fourth outside member mounted on said first barof said means for measuring the depth of penetration of the indentorinto the surface of material; at least one contact land provided in saidfourth outside member, said sensor of said at least one pick-up formeasuring the depth of penetration of the indentor into the surface ofmaterial being engageable with said contact land.
 6. An apparatusaccording to claim 5, comprising:at least one of said outside membershaving an auxiliary hole; one of said bars of said frame of said meansfor measuring the depth of penetration of the indentor into the surfaceof material having at least one hole in the peripheral portion thereof;at least one bearing being received in at least one of said holes of oneof said bars of said frame; at least one guide pin having a first endand a second end, the first end being received in the auxiliary hole ofone of said outside members, the second end being received in said atleast one bearing of one of said bars of said frame.
 7. An apparatusaccording to claim 6, wherein said at least two guide pins arepositioned on either side of the longitudinal plane of symmetry of saiddynamometric gauge.
 8. An apparatus according to claim 1, comprisingsaid frame of said means for measuring the depth of penetration of theindentor into the surface of material; said first bar of said framehaving a hole in said central portion thereof; said second bar of saidframe having a hole in said central portion thereof; a first bearingreceived in said hole of said first bar of said frame; said center plateof said rod being journalled in said first bearing; a second bearingreceived in said hole of said second bar of said frame, said shank ofsaid rod being journalled in said second bearing.
 9. An apparatusaccording to claim 8, comprising: said at least two pick-ups formeasuring the load at the indentor positioned on either side of thelongitudinal plane of symmetry of said dynamometric gauge;said at leasttwo pick-ups for measuring the depth of penetration of the indentor intothe surface of material positioned on either side of said dynamometricgauge.
 10. An apparatus according to claim 8, comprising;a first outsidemember mounted on one of said branches of said dynamometric gauge; atleast one main hole in said first outside member, said body of said atleast one pick-up for measuring the load at the indentor being rigidlysecured in said hole; a second outside member mounted on said otherbranch of said dynamometric gauge; at least one contact land provided insaid second outside member, said sensor of said at least one pick-up formeasuring the load at the indentor being engageable with said contactland; a third outside member mounted on said first branch of saiddynamometric gauge; at least one main hole in said third outside member,said body of said at least one pick-up for measuring the depth ofpenetration of the indentor into the surface of material being rigidlysecured in said hole; a fourth outside member mounted on said first barof said means for measuring the depth of penetration of the indentorinto the surface of material at least one contact land provided in saidfourth outside member, said sensor of said at least one pick-up formeasuring the depth of penetration of the indenter into the surface ofmaterial being engageable with said contact land.
 11. An apparatusaccording to claim 10, comprising:at least one of said outside membershaving an auxiliary hole; one of said bars of said frame of said meansfor measuring the depth of penetration of the indentor into the surfaceof material having at least one hole in the peripheral portion thereof;at least one bearing being received in at least one of said holes of oneof said bars of said frame; at least one guide pin having a first endand a second end, the first end being received in the auxiliary hole ofone of said outside members, the second end being received in said atleast one bearing of one of said bars of said frame.
 12. An apparatusaccording to claim 11, wherein said at least two guide means arepositioned on either side of the longitudinal plane of symmetry of saiddynamometric gauge.
 13. An apparatus according to claim 8, saidapparatus also comprising an elastic member having a first side and asecond side opposed to each other, the first side being attached to saidspindle of said means for loading the indentor on the side if said innersurface of said second branch of said dynamometric gauge, the secondside being attached to said second bar of said frame of said means formeasuring the depth of penetration of the indentor into the surface ofmaterial.
 14. An apparatus according to claim 13, wherein said elasticmember is in the form of an annular spring.
 15. An apparatus accordingto claim 1, comprising: said at least two pick-ups for measuring theload at the indentor positioned on either side of the longitudinal planeof symmetry of said dynamometric gauge;said at least two pick-ups formeasuring the depth of penetration of the indentor into the surface ofmaterial positioned on either side of said dynamometric gauge.
 16. Anapparatus according to claim 15, comprising:a first outside membermounted on one of said branches of said dynamometric gauge; at least onemain hole in said first outside member, said body of said at least onpick-up for measuring the load at the indentor being rigidly secured insaid hole; a second outside member mounted on said other branch of saiddynamometric gauge; at least one contact land provided in said secondoutside member, said sensor of said at least one pick-up for measuringthe load at the indentor being engageable with said contact land; athird outside member mounted on said first branch of said dynamometricgauge; at least one main hole in said third outside member, said body ofsaid at least one pick-up for measuring the depth of penetration of theindentor into the surface of material being rigidly secured in saidhole; a fourth outside member mounted on said first bar of said meansfor measuring the depth of penetration of the indentor into the surfaceof material; at least one contact land provided in said fourth outsidemember, said sensor of said at least one pick-up for measuring the depthof penetration of the indentor into the surface of material beingengageable with said contact land.
 17. An apparatus according to claim16, comprising:at least one of said outside members having an auxiliaryhole; one of said bars of said frame of said means for measuring thedepth of penetration of the indentor into the surface of material havingat least one hole in the peripheral portion thereof; at least onebearing being received in at least one of said holes of one of said barsof said frame; at least one guide pin having a first end and a secondend, the first end being received in the auxiliary hole of one of saidoutside members, the second end being received in said at least onebearing of one of said bars of said frame.
 18. An apparatus according toclaim 17, wherein said at least two guide pins are positioned on eitherside of the longitudinal plane of symmetry of said dynamometric gauge.19. An apparatus according to claim 15, said apparatus also comprisingan elastic member having a first side and a second side opposed to eachother, the first side being attached to said spindle of said means forloading the indentor on the side of said inner surface of said secondbranch of said dynamometric gauge, the second branch being attached tosaid second bar of said frame of said means for measuring the depth ofpenetration of the indentor into the surface of material.
 20. Anapparatus according to claim 19, wherein said elastic member is in theform of an annular spring.
 21. An apparatus according to claim 15,wherein said pick-ups for measuring the load at the indentor, saidpick-ups for measuring the depth of penetration of the indentor into thesurface of material and said drive for moving the spindle of said meansfor loading the indentor are electrical.
 22. An apparatus according toclaim 21, comprising said means for loading the indentor; a worm gearingof said means for loading the indentor coupled to said electric drivefor moving the spindle; a ball-and-screw gearing of said means forloading the indentor operatively connected to said worm gearing andprovided on said periphery of said spindle.
 23. An apparatus accordingto claim 1, comprising:a first outside member mounted on one of saidbranches of said dynamometric gauge; at least one main hole in saidfirst outside member, said body of said at least one pick-up formeasuring the load at the indentor being rigidly secured in said hole; asecond outside member mounted on said other branch of said dynamometricgauge; at least one contact land provided in said second outside member,said sensor of said at least one pick-up for measuring the load at theindentor being engageable with said contact land; a third outside membermounted on said first branch of said dynamometric gauge; at least onemain hole in said third outside member, said body of said at least onepick-up for measuring the depth of penetration of the indentor into thesurface of material being rigidly secured in said hole; a fourth outsidemember mounted on said first bar of said means for measuring the depthof penetration of the indentor into the surface of material; at leastone contact land provided in said fourth outside member, said sensor ofsaid at least one pick-up for measuring the depth of penetration of theindentor into the surface of material being engageable with said contactland.
 24. An apparatus according to claim 23, comprising:at least one ofsaid outside members having an auxiliary hole; one of said bars of saidframe of said means for measuring the depth of penetration of theindentor into the surface of material having at least one hole in theperipheral portion thereof; at least one bearing being received in atleast one of said holes of one of said bars of said frame; at least oneguide pin having a first end and second end, the first end beingreceived in the auxiliary hole of one of said outside members, thesecond end being received in said at least one bearing of one of saidbars of said frame.
 25. An apparatus according to claim 24, wherein saidat least two guide pins are positioned on either side of thelongitudinal plane of symmetry of said dynamometric gauge.
 26. Anapparatus according to claim 24, said apparatus also comprising anelastic member having a first side and a second side opposed to eachother, the first side being attached to said spindle of said means forloading the indentor on the side of said inner surface of said secondbranch of said dynamometric gauge, the second side being attached tosaid second bar of said frame of said means for measuring the depth ofpenetration of the indentor into the surface of material.
 27. Anapparatus according to claim 26, wherein said elastic member is in theform of an annular spring.
 28. An apparatus according to claim 24,wherein said pick-ups for measuring the load at the indentor, saidpick-ups for measuring the depth of penetration of the indentor into thesurface of material and said drive of the spindle of said means forloading the indentor are electrical.
 29. An apparatus according to claim28, comprising said means for loading the indentor; a worm gearing ofsaid means for loading the indentor coupled to said electric drive formoving the spindle; a ball-and-screw gearing of said means for loadingthe indentor operatively connected to said worm gearing and provided onsaid periphery of said spindle.
 30. An apparatus according to claim 23,said apparatus also comprising an elastic member having a first side anda second side opposed to each other, the first side being attached tosaid spindle of said means for loading the indentor on the side of saidinner surface of said second branch of said dynamometric gauge, thesecond branch being attached to said second bar of said frame of saidmeans for measuring the depth of penetration of the indentor into thesurface of material.
 31. An apparatus according to claim 30, whereinsaid elastic member is in the form of an annular spring.
 32. Anapparatus according to claim 23, wherein said pick-ups for measuring theload at the indentor, said pick-ups for measuring the depth ofpenetration of the indentor into the surface of material and said drivefor moving the spindle of said means for loading the indentor areelecrical.
 33. An apparatus to claim 32, comprising said means forloading the indentor; a worm gearing of said means for loading theindentor coupled to said electric drive for moving the spindle; aball-and-screw gearing of said means for loading the indentoroperatively connected to said worm gearing and provided on the peripheryof said spindle.
 34. An apparatus according to claim 1, said apparatusalso comprising an elastic member having a first side and a second sideopposed to each other, the first side being attached to said spindle ofsaid means for loading the indentor on the side of said inner surface ofsaid second branch of said dynamometric gauge, the second side beingattached to said second bar of said frame of said means for measuringthe depth of penetration of the indentor into the surface of material.35. An apparatus according to claim 34, wherein said elastic member isin the form of an annular spring.
 36. An apparatus according to claim34, wherein said pick-ups for measuring the load at the indentor, saidpick-ups for measuring the depth of penetraton of the indentor into thesurface of material and said drive of the spindle of said means forloading the indentor are electrical.
 37. An apparatus according to claim36, comprising said means for loading the indentor; a worm gearing ofsaid means for loading the indentor coupled to said electric drive formoving the spindle; a ball-and-screw gearing of said means for loadingthe indentor operatively connected to said worm-gearing and provided onsaid periphery of said spindle.
 38. An apparatus according to claim 1,wherein said pick-ups for measuring the depth of penetration of theindentor into the surface of material and said drive for moving thespindle of said means for loading the indentor are electrical.
 39. Anapparatus according to claim 38, comprising said means for loading theindentor; a worm gearing of said means for loading the indentor coupledto said electric drive for moving the spindle; a ball-and-screw gearingof said means for loading the indentor operatively connected to saidworm gearing and provided on said periphery of said spindle.